This invention relates generally to radiotelephone systems and, in particular, to a radiotelephone system having multi-carrier, wideband code division multiple access (WCDMA) capability.
A proposed IS-95 third generation (3G) radiotelephone system has a wideband, spread spectrum radio interface that uses CDMA technology. The system is expected meet all of the requirements for the next generation evolution of the current TIA/EIA-95-B family of standards. This includes providing support for the following: a wide range of operating environments (indoor, low mobility, full mobility, and fixed wireless); a wide performance range (from voice and low speed data to very high speed packet and circuit data services); and a wide range of advanced services (including voice only, simultaneous voice and data, data only, and location services). Support is also provided for an advanced Multimedia Quality of Service (QoS) Control capability supporting multiple concurrent voice, high speed packet data, and high speed circuit data services, along with sophisticated QoS management capabilities. A modular structure is proposed to support existing Upper Layer Signaling protocols as well as a wide range of future third generation Upper Layer Signaling protocols. The proposed system is also expected to provide a seamless interoperability and handoff with existing TIA/EIA-95-B systems, and to provide a smooth evolution from existing TIA/EIA-95-B based systems (including support for overlay configurations within the same physical channel as existing TIA/EIA-95-B systems.) The proposed system will also support highly optimized and efficient deployments in clear spectrum (in cellular, PCS, and IMT-2000 spectrum), and will offer support for existing TIA/EIA-95-B services, including speech coders, packet data services, circuit data services, fax services, Short Messaging Services (SMS), and Over the Air Activation and Provisioning.
Of particular interest to the teaching of this invention is an ability to provide Nxc3x971.25 MHz (N=1, 3, 6, 9, and 12) Multi-Carrier systems that can be deployed as an overlay on up to N 1.25 MHz TIA/EIA-95-B carriers. In this configuration the resulting system can concurrently provide both second generation and third generation services to second generation (TIA/EIA-95-B) and third generation (IS-95 3G) mobile stations. When operated in the overlay configuration the second and third generation systems share common pilot channels, and can optionally share common paging channels. The third generation spread spectrum system can also be deployed in another set of channels within the same or in a different frequency band.
In general, the IS-95 3G system provides the ability to coexist with TIA/EIA-95-B in the same frequency channel via the overlay configuration, as well as an ability to coexist with TIA/EIA-95-B systems in the same frequency band (e.g., cellular or PCS).
It is known in the art, in the multi-carrier or multi-channel context, that information symbols are transmitted or more specifically de-multiplexed uniformly. This is because the symbol transmission rate is the same for all the sub-carriers in the multi-carrier system. In such an arrangement, the overall performance of the spread spectrum overlay is limited by the most loaded subcarrier within the multi-carrier system.
It is also known in the art, in the multi-carrier context, that the information symbols can be transmitted based on a base transmission rate and multiples of the base rate. In such an arrangement, there is no formalized method of choosing symbol transmission rates, and no parameter values upon which the symbol transmission rates are formulated. The symbol transmission rates are numbers which are finite and discrete.
In these systems, the symbol transmission rate cannot be readily determined in a domain of rational numbers in a continuous manner.
It is a first object and advantage of this invention to non-uniformly distribute information signals amongst different channels in a multi-channel wireless communication system using a spread spectrum method.
It is a second object and advantage of this invention to determine a symbol transmission rate for each channel based upon each channel""s parameters, which are a function of factors determined with and without transmitted information, respectively.
It is a third object and advantage of this invention to determine a symbol transmission rate continuously on a subset, interval, or domain of rational numbers.
It is a fourth object and advantage of this invention to determine and formalize a quantity which is independent of information symbols or signals transmitted within a multi-channel system.
It is a further object and advantage of this invention to determine and formalize a quantity which is dependent upon information symbols or signals transmitted within a multi-channel system.
The foregoing and other problems are overcome and the objects and advantages are realized by methods and apparatus in accordance with embodiments of this invention.
In one aspect this invention teaches a wireless telecommunications system that includes at least one base station, at least one mobile station, and a data distribution system in the base station for non-uniformly distributing data amongst a plurality of subchannels, that are overlaid upon one or more underlying channels, before transmission of the plurality of subchannels to the mobile station. The data distribution system non-uniformly distributes the data in accordance with a total load that is already present in each of the subchannels due to the presence of the underlying channels.
In a further aspect this invention teaches a multi-channel wireless communication system of a type that utilizes a first spread spectrum communication subsystem with one or more subchannels capable of co-existing with channels of a second spread spectrum communication subsystem. In a transmission station of the system there is provided a data distributor for distributing information signals non-uniformly amongst the subchannels based upon a plurality of criteria and, coupled to outputs of the data distributor, circuitry for spreading and transmitting the information signals to the plurality of subchannels. The plurality of criteria are comprised of a first noise-related factor N0 and a second noise-related factor N2G, wherein the first noise-related factor N0 is independent of information signals transmitted within the overlaid channels, and wherein the second factor N2G relates to one subchannel and is dependent upon information signals transmitted within the overlaid channels.
In the preferred embodiment the first spread spectrum subsystem has wider transmission bandwidth than the second spread spectrum subsystem, and the plurality of subchannels have a set of carrier frequencies with bandwidth that either overlaps one another or that does not overlap one another.
The data distributor operates with a set of symbol transmission rates fi for an ith channel, which is dependent upon: a positive integer M which denotes a total number of subchannels, the first noise related factor N0, a second factor N2G that pertains to the subchannel, and a desired total transmission rate r, in accordance with       f    i    =            r      ·              (                              N            0                    +                                    1                              M                -                1                                      ⁢                          xe2x80x83                        ⁢                                          ∑                                  j                  =                  1                                M                            ⁢                              N                                                      2                    ⁢                    G                                    -                  j                                                                    )                    (                        M          ·                      N            0                          +                              ∑                          j              =              1                        M                    ⁢                      N                                          2                ⁢                G                            -              j                                          )      
wherein in the summation constituting part of the numerator, the j""s do not include i.
The data distributor is controlled by a controller that operates with one of static criteria over an interval of time, or dynamic criteria that vary as the loading of the overlaid channels varies over an interval of time.
A spread spectrum code division multiple access wireless telecommunications system in accordance with this invention thus includes at least one base station, a plurality of mobile stations located in a region served by said at least one base station, and a data distribution system in the base station for non-uniformly distributing information bits to be transmitted amongst X first spread spectrum system channels. At least one of the X channels coexists with a second spread spectrum system channel. The data distribution system non-uniformly distributes the information bits in accordance with a first noise factor that is substantially independent of transmitted information bits and X second noise factors individual ones of which are associated with information bits being transmitted in one of said X first spread spectrum channels.